A breathing circuit is typically operated in one of two modes of operation: a half-closed mode of operation or as an extensively closed circuit. In the half-closed mode of operation the quantity of breathing gas exceeds the quantity that is taken up by a patient. The excess breathing gas is released from the breathing circuit into an anesthetic removal system during the phase of expiration by the patient. In the mode of operation with the closed breathing circuit, the breathing gases are essentially reprocessed by the CO2 absorber. A suitable absorbent, for example, soda lime, is used for this. The breathing circuit typically comprises an inspiratory breathing gas duct and an expiratory breathing gas duct for making available breathing gas for the patient. The breathing gas is enriched here with anesthetic by means of an anesthetic dispensing means. The inspiratory breathing gas duct and the expiratory breathing gas duct are connected to one another via a so-called Y-piece, which is used via a connected flexible tube to pass on breathing gas to the patient. Up to 5 L of breathing gas are contained in a breathing circuit. Breathing gas of the previous patient may still be present in the breathing circuit between two patient treatments. The breathing circuits of the anesthesia devices can be rinsed out pneumatically, as a rule, only poorly. In particular, intolerance of the breathing gas already used may develop in the next patient. A complicated processing of the breathing circuit by means of a connected simulation lung with simultaneous feed of breathing gas from the breathing gas supply system is, as a rule, necessary for this. To ensure that no anesthetic is present in the components of the breathing circuit, the breathing circuit of the anesthesia device must therefore be rinsed completely. In particular, this measure is significant for the case in which another anesthetic is to be used for the next patient.
Both an anesthesia device and a process for operating the anesthesia device, with which a gas flow of a rinsing gas from a breathing gas supply system is controlled by means of a control means, are disclosed in WO 2008/000 299 A1. Rinsing of the anesthetic from the anesthesia device may now take place when the anesthesia device is not connected to a patient. Gas from the central gas supply system of a hospital is typically used for this. The use of this technical breathing gas for reprocessing the breathing circuit is very cost-intensive.